The instrumentation requested in this proposal is a fluorescence- activated cell sorter (FACS) system. A FACS uses laser technology to examine fluorescently tagged intracellular and cell surface proteins and DNA content of live or fixed individual cells (FACS analysis). In addition, the equipment is designed to sort cells with fluorescently tagged proteins and/or DNA content (FACS sorting). The major component of the system are the laser bench and optics, a UV and an argon laser, detectors, controller, and computer/software/printer. The common thread running through the research described in this proposal is the need for analyzing and sorting single cells; however, the areas of biomedical research requiring cell analysis/cell sorting are diverse. NIH-funded projects under investigation at U.S.D. which would benefit from better access to a FACS include studies of: . Assembly of class I major histocompatibility complex molecules (which present antigens to immune T cells), and interference with this assembly process by virus proteins . Effects of lentiviruses on equine and human cells. . Mechanisms responsible for tissue-specific, differential aldehyde dehydrogenase gene expression, which is inducible in the liver upon exposure to toxins and during carcinogenesis. . Coupling of exit from the cell cycle to differentiation for oligodendrocytes (the cells in the central nervous system which produce myelin) . Alterations in cardiac myocyte proteins during cardiac hypertrophy and congestive heart failure